On 4 February 2010 09:13, G. Ken Holman
<gkholman(_at_)cranesoftwrights(_dot_)com> wrote:
At 2010-02-04 09:04 +0000, Andrew Welch wrote:
Just to check that by "valid potential QName" you mean a string that is
in
the lexical space of xs:QName and will therefore constitute a valid
QName
provided the prefix is in scope?
($x castable as xs:QName) will not work because (a) it also tests
whether
the prefix is in scope, and (b) to avoid the issues of it therefore
being
context-sensitive, the W3C spec says this is only allowed if the
argument
($x) is a string literal.
So you do need to use the regex approach.
Could you do a fn:prefix-from-QName($x) = fn:in-scope-prefixes(.)
check before doing the castable as check?
Nope:
http://www.w3.org/TR/2007/REC-xpath20-20070123/#id-castable
"[if] the input argument of the expression is of type xs:string but it is
not a literal string, the result of the castable expression is false."
To help me understand that :-) can you provide an example of a user
constructed string that is not a string literal?
For example, tokenizing a string into a sequence of strings... they
are all string literals aren't they?
--
Andrew Welch
http://andrewjwelch.com
Kernow: http://kernowforsaxon.sf.net/
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